Cadell Jeanson Raja (30), who was working as an animator for an Australian firm, was arrested from Thiruvananthapuram railway station while he was discreetly boarding a train to Chennai, a senior police officer said. The police have taken him to an undisclosed location for questioning.

Half-burnt and badly mutilated bodies were recovered on Sunday morning after some of the local residents complained of smoke billowing from the house situated just 500 m away from the official residence of the Kerala chief minister.

While three bodies were charred, another was chopped and kept in a bag at the multi-storeyed house. Those killed were retired cardiologist Dr Jean Padma, her husband Professor Raj Thankam, their daughter Caroline and a relative Lalitha. Caroline was on vacation from China where she was studying medicine.

The police also recovered a half-burnt dummy from the house. The dummy bore similarities to Cadell and it is suspected he could have left the dummy inside the house to create an impression that all five people in the house were murdered. Two weapons used for the alleged murders, a can of petrol and blood-stained clothes were seized from the house.

The police and relatives are clueless about the possible motive for the murder. There was no sign of break- in or forcible entry in the house.

The police later said the absconding son might have committed the murders. The reclusive family was financially sound and neighbours and relatives were unaware of any possible tension in the family.

Prof Thankam’s brother Jose reportedly told the police that his sister was unavailable on the phone since Thursday and added that Cadell had told him that his parents were in Kanyakumari. The police suspect that the crime was committed at least two days ago and Cadell could have slipped out when he failed to burn bodies and the fire spread quite rapidly within the house. When the maid employed by the aged couple came for routine work Cadell reportedly told her that the family left for Tamil Nadu and asked her to come after three days.

Local residents said the reclusive Cadell was a total stranger in the colony where he grew up. “No one has been seen him closely to tell if he had any character flow or weakness. It was a rude shock for the state capital on Palm Sunday,” said a neighbour.